The invention relates to a vehicle occupant restraint system comprising an inflatable knee airbag. The invention further relates to an automotive vehicle comprising such vehicle occupant restraint system. Finally the invention also relates to a method of protecting a vehicle occupant.
The inflation and discharge behavior of airbags is tested by crash test dummies in impact tests. Crash test dummies are life-size dummies simulating the human body. In order to duly take the different anatomic factors of real persons into account during simulations, the tests are usually carried out with three different dummies. The “50 percent male” having a body height of 175 cm and a weight of 78 kg is supposed to generally correspond to a vehicle occupant of “normal” size, the “95 percent male” having a body height of 188 cm and a weight of 101 kg is supposed to correspond to a tall vehicle occupant and the “5 percent female” having a body height of 152 cm and a weight of 54 kg is supposed to correspond to a small vehicle occupant.
From DE 10 2004 009 013 A1 a side impact restraint device for protecting an occupant being seated on a vehicle seat in a vehicle comprising an airbag is known which adapts to the build of the vehicle occupant. The airbag deploys between a side structure of the vehicle and the vehicle occupant and includes a first vent hole arranged in a zone of the airbag facing the vehicle occupant. The vertical position of the vent hole is selected so that it is not covered by the upper part of the body of a small size vehicle occupant but is definitely covered by a large size vehicle occupant. Thus for a small size vehicle occupant a lower internal pressure is resulting than for a large size vehicle occupant.
In EP 1 279 565 A1 a generic occupant protection device comprising a knee airbag is shown in which a vent hole is provided in an upper end portion. The vent hole interacts with a passenger airbag disposed above the knee airbag. When the legs of the vehicle occupant strike the deployed knee airbag and the vent hole initially is not yet covered by the passenger airbag, gas may flow out of the vent hole. In this way the impact exerted on the vehicle occupant is damped. However, as soon as the deployed passenger airbag covers the vent hole, the gas discharge from the vent hole is restricted so that a minimum internal pressure of the knee airbag is maintained for a quite long period of time.